Ultrasonic Detection Of Polymer PVT And Theoretical Studies

Pressure, volume and temperature （P-V-T） has a direct impact on theproduction, processing and application of polymers. It is very significantto understand the basic rules and to develop the on-line detection wayswhich can be used in industry. Conventional methods are difficult to beapplied to actual projects, non-destructive online detection exhibits broadprospects. In this paper, ultrasonic testing method was used tocharacterize polymer PVT. Specific characterization methods wereobtained on quantitative models and experimental data-fitted relations.In this article, the polymer PVT data and the ultrasonic signal dataare simultaneously measured under steady state conditions. Thequantitative relationship between specific volume and ultrasonic velocityare summarized after analyzing the experimental data. Through Taitempirical equation, the Flory-Orwoll-Vrij model （FOV equation）,Prigogine "square well" cell model （CM equation）, Dee and Walsh modified cell model （MCM equations）, Sanchez-Lacombe lattice-fluidmodel （SL equation）, and the Hartmann-Haque model （HH equations）,the effects of polymer structure, blend component and filler content onthe transferred ultrasonic signals and parameters’ value state equation.（1） Crystalline high-density polyethylene （HDPE） was used as anexample to analyze the relationship between polymer PVT and ultrasonicsignals. It was shown that transition temperature of PVT curvecorresponds with the extreme values of ultrasonic amplitude and velocitywhich is close to the endothermic peak （T_m） of its DSC curve. The shapeof specific volume curve is similar to that of ultrasonic velocity curveillustrating that the latter can quantatively describe specific volume.This fact is also fitful to polymer blends （PP/HDPE） and polymer-filledsystem （PP/CaCO₃）.（2） The parameter’s values of state equation were calculated for thethree types of material systems by numerical fitting experimental data.The influences of composition for polymer blends and that of fillercontent for polymer-filled system on the ultrasonic signals and theequation of state parameters were analyzed showing certain regularity.Both of ultrasonic signal and the equation of state parameters can wellreflect the compatibility of polymer blends.（3） Five sets of equations were developed to quantitatively describethe relations between ultrasonic velocity and specific volume for three types of complex polymer materials. Their comparison told thatV=c^-1/3.F^-7/6 is applicable to all materials when F-value varies linearlywith filler content.